<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <button id="btn">获取数据</button>

  <script>
    let btn = document.getElementById('btn');
    btn.addEventListener('click', () => {
      fetch('http://localhost:3000')
      .then(res => res.json())
      .then((res) => {
        console.log(res);
      })
    })

  </script>
</body>
</html>